On his 60th, he swam from Alcatraz Island to Fisherman’s Wharf in San Francisco handcuffed, shackled and towing a 1,000-pound boat. His 70th was marked by pulling 70 boats carrying 70 people for a mile-and-a-half in rough waters – shackled.

And on his 80th birthday, he shot an 80 in golf.

“I had people lifting weights when they were in their 80s and people thought I was nuts back then,” LaLanne said of his fitness fixation, which he’s been nurturing for more than 60 years.

So for his 85th today, LaLanne wanted to do something equally awesome, like swimming from Catalina Island to Los Angeles – 26 miles – under water.

“Jack’s got a 29-inch waist, his chest is about 47-48 inches, and his arms are about 16-and-a-half,” said longtime friend and partner Richie Ornstein, a former NYPD cop.

“He still keeps himself in fantastic shape. He swims every day, he works out with weights, he plays golf a few times a week.”

Ornstein said that using LaLanne’s new “fitness age” gauge – determining age by what exercises you can do – the exercise guru is 29, his wife, 28.

Not bad for an old-timer.

But then again, LaLanne’s whole life has been about fitness. He was born Francois Henri LaLanne to French immigrants, grew up on a sheep farm in Bakersfield, Calif., then moved with his family to Oakland.

He opened his first health club in 1936 in Oakland and in 1951, went on TV with the first-ever exercise program on the small screen.